Variable inductance device



Nov. 24, 1959 J. J. ANTALEK ETAL VARIABLE INDUCTANCE DEVICE Filed July 6, 1955 2 Sheets-Sheet l ZFEB I v i I NVENT S JOHN J. ANTALEK and ROBERT W. SAV/LLE 7 WM, l56

ATTOE/QEY? NOV. 24, 1959 J ANTALEK ETAL 2,914,276

VARIABLE INDUCTANCE DEVICE Filed July 6, 1955 2 Sheets-Sheet 2 m veflrogs JOHN J. AMTALEK am/ ease/e7- WSAV/LLE 07",) ,dww MUM a) ATTOKAJE Y7 United States Patent VARIABLE INDUCTAN CE DEVICE John J. Antalek, Chicago, and Robert W. Saville, Glenview. Ill., assignors to Radio Industries, Inc., Chicago, Ill., a corporation of Illinois Application July 6,1955, Serial No. 520,331

Claims. (Cl. 248-27) The present invention relates to variable inductance devices of the type having one or more conductive coils mounted on a tubular coil form in the bore of which a threaded core member is adjustably positioned, and more particularly to a coil form which facilitates initial fabrication of the inductance device and further facilitates attachment thereof to a support member such, for example, as a chassis.

With the advent of printed circuit techniques, complete mechanization of production lines for assembling electrical communication equipment may be economically achieved, and therefore, it becomes desirable to provide a variable inductance device which is susceptible to automatic assembly thereof on a printed circuit or conventional chassis. Also, in order to minimize the manufacturing cost of the individual variable inductance devices, the coil form therefor should be such as to be suitable for use in automatic equipment for winding the various coils thereon.

Therefore, an important object of the present invention is to provide a new and improved variable inductance device suitable for use in equipment which is assembled on mechanized production lines.

Another object of the present invention is to provide a variable inductance device having improved means for facilitating attachment thereof to a printed circuit chassis or other support member.

Still another object of the present invention is to provide a variable inductance device having an improved coil form for facilitating winding of the coil thereon by automatic machinery.

A further object of the present invention is to provide a new and improved coil form which enables greater ease in the fabrication of a variable inductance device than is possible with coil forms of the prior art type.

Briefly, the above objects are realized in accordance with the present invention by the provision of a molded unitary tubular coil form having an enlarged cylindrical portion terminating in a collar which extends outwardly from one end of the form. A plurality of deformable ribs, integral with the collar portion of the form, are disposedon the outside thereof and extend parallel with the principal axis of the form. Where desirable, a plurality of protrusions are provided near the end of the collar to aid in firmly maintaining the variable inductance device secured to a support member. So as to facilitate the winding of a conductive wire on the form by means of automatic coil winding machinery, both ends of the coil form are serrated and a plurality of notches are provided in that end of the enlarged cylindrical portion which is displaced from the collar.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof will best be understood by reference to the following detailed description taken in connection with the accompanying drawings in which:

Fig. l is a front elevational view of a variable induct- 2,914,276 Patented Nov. 24, 1959 ance device embodying the present invention which is assembled to a chassis, only a fragmentary portion of which chassis is shown, and such portion being in crosssection;

Fig. 2 is a sectional view of the arrangement of Fig. 1 taken along the line 22 thereof;

Fig. 3 is an enlarged sectional view showing the variable inductance device of the present invention while it is being inserted into an aperture in a chassis;

Fig. 4 is a sectional view of the device of Fig. 3 taken along the line 4-4 thereof;

Fig. 5 is an exploded perspective view of an alternative embodiment of the present invention;

Fig. 6 is a fragmentary perspective view of the device shown in Fig. 5 looking at the bottom portion thereof;

Fig. 7 is a plan view partially in section of the inductance device of Fig. 5 assembled to a chassis;

Fig. 8 is a fragmentary sectional view of the assembly of Fig. 7 taken along the line 88 thereof assuming the entire unit to be shown therein; and

Fig. 9 is a fragmentary elevational view of an alternative embodiment of the invention showing an inductance device mounted on a chassis, a portion of the device being broken away and another portion being shown in section. Referring now to the drawings, and more particularly to Fig. 1 thereof, there is shown a variable inductance device 10 consisting of a tubular coil form 11 having an enlarged, cylindrical lower portion 12 on which is mounted a plurality of conductive terminal members 13. The coil form 11 is molded of an insulating material, suitably a plastic, and in the particular device shown, a pair of helical coils 15 and 16, which may conveniently be formed of copper wire, are wound on the coil form 11 having the ends thereof conductively connected as by brazing to different pairs of the terminal members 13. It will be understood that although the inductance device shown in Fig. 1 to illustrate the invention is a transformer utilizing a pair of coils 15 and 16, a greater or lesser number of coils may be provided on the form 11, if desired.

Although the manner in which the inductance of the windings 15 and 16 and the magnetic coupling therebetween does not constitute a part of the present invention and, therefore, is not shown in the drawings, it will be understood by those skilled in the art that a ferromagnetic core member conventionally shaped in the form of a cylinder is movably supported within the upper portion of the coil form 11 thereby to intercept the magnetic field produced by each of the windings 15 and 16.

A collar member 18 extends downwardly from the enlarged portion 12 and, being of lesser diameter than the portion 12, defines an annular shoulder 19 on the coil form 11. A portion 21 of a printed circuit chassis or of a metal chassis, as the case may be, is provided with a circular aperture 22 having a diameter slightly exceeding that of the collar 18 but being considerably less than the diameter of the enlarged portion 12. Therefore, as shown in Fig. 1, when the variable inductance device 10 is assembled to the chassis 21 with the collar 18 located within the aperture 22, the shoulder 19 engages the top of the chassis 21 in an area surrounding the aperture 22 thereby to support the device 10 at the top of the chassis 21.

in order to facilitate the attachment of the variable inductance device 10 to the chassis 21 while insuring that the device 10 is firmly attached thereto, a plurality of outwardly extending ribs 24 are provided on the coliar 18, the ribs 24 extending in a direction parallel with the principal axis of the coil form 11. As best shown in Fig. 4, the ribs are semi-cylindrical in shape having an out able for this purpose. I

In order to assemble the variable inductance device 10 to a chassis 21, the collar 18 is inserted into the aperture 22, and as best shown in Fig. 3, the ribs 24 are compressed as they pass into the aperture 22. Once the device has been fully inserted into the aperture 22 so that the shoulder 19 engages the top of the chassis 21, the lower portions of the ribs 24 which extend a considerable distance below the bottom of the chassis 21 expand outwardly because of the natural elasticity thereof so as to provide an upwardly facing shoulder 2411 on each rib which engages the bottom of the chassis 21 in the area adjoining the aperture 22. Removal of the device 10 is thus prevented by the shoulders 24a on ribs 24 and rotation thereof is also prevented by the engagement of the intermediate portions of the ribs 24 with the walls of the aperture 22.

In the event that the variable inductance device 10 is to be used in equipment which is subjected to excessive vibration as Well as severe shocks, it may be desirable to provide securing means in addition to the ribs 24 to insure that the device 10 is not jarred loose from the chassis 21. Referring to Figs. to 8, inclusive, there is shown a coil form 11a which is an alternative embodiment of the coil form 11, and wherein means in the form of a plurality of protuberances 30 are provided on the collar 18 for coaction with the chassis 21 to maintain the device in engagement with the chassis 21.

In this embodiment, the collar 18 is provided with a plurality of outwardly directed protuberances 36' which are spaced from the shoulder 19 by a distance slightly exceeding the thickness of the chassis 21, and with an additional protuberance 31 which extends from the enlarged portion 12 to the bottom of the coil form 11a. Adjacent the aperture 22 in the chassis 21 there is provided a plurality of slotted recesses 30a which are shaped and positioned so as to receive therein the protuberances 30 when the form 11a is placed on the chassis 21 with the collar 18 disposed in the aperture 22. An elongated recess 31a is positioned in the board 21 so as to receive the protuberance 31 when the protuberances 30 are aligned with the recesses 30a. The width of the recess 31a exceeds that of the protuberance 31 to permit rotation of the form 11a through a limited angle after it is inserted in the aperture 22 thereby to move the protuberances 30 out of alignment with the recesses 343a and partially beneath the chassis 21.

When, therefore, the coil form is placed on the chassis 21 such that the collar extends through the aperture 22 and the protuberances 30 and 31 are in alignment with their respective recesses in the baseboard 21, the coil form 11 may be inserted until the shoulder 19 thereon engages the top of the chassis 21. At this time the coil form 11 is rotated clockwise with respect to the sup port 21 as viewed from the top, so that the protuberances 30 extend beneath the support 21 out of alignment with their respective recesses 30a (Fig. 7).

Since, as the collar 13 is pressed into the aperture 22 the ribs 24 thereon are compressed as described above, when the device 10 is rotated with respect to the chassis 21, the shoulder 24a, which appears on the ribs 24 as they mold themselves in place after having been compressed, and the intermediate portion of the ribs 24 respectively bear upwardly and outwardly against the wall of the aperture 22 in the chassis 21 thereby to prevent spurious rotation of the variable inductance device 10.

Referring to Fig. 9, a plastic coil form 11b is provided with a collar 18b having a plurality of ribs 37 substantially identical with the ribs 24 in the device of Fig. l and with a protuberance 38 corresponding in every detail to the protuberance 31 in the coil form 11a of Fig. 5. The collar 18b is disposed in an opening 39 in the chassis 40, it being understood that the opening 39 has a slot-like portion for receiving the protuberance 38. Therefore, the protuberance 38 and the corresponding recess therefor in the chassis 40 provides indexing means to insure proper positioning and orientation of the form 11b on the chassis 40.

In order to provide additional means for securing the device 11b to the chassis 40, an annular semi-toroidal protrusion 42 is provided on the collar 18b. The annulus 42 lies in a plane parallel to that occupied by the shoulder 19b on the form 1112 and is spaced from this shoulder by a distance somewhat exceeding the thickness of the chassis to be used therewith. The annulus 42 being integral with the collar 18b is deformable and since the outer diameter thereof exceeds that of the opening 39 in the chassis, as the collar 18b is inserted into the opening 39 the annulus 42 deforms as it passes through the opening 39 in the chassis 40. When the shoulder 19b engages the top face of the chassis 40, the annulus 42 is disposed below the chassis 40 out of contact therewith and thus expands and bends toward its initial state, thereby removably holding the form 111; on the chassis 40.

As mentioned above, it is desirable if not'altogether necessary to automatically and rapidly wind the coils 15 and 16 on the coil form during the fabrication of the variable inductance device 10. Furthermore, it is desirable that a large number of such devices be simultaneously wound on a single winding machine. In one conventional type of apparatus for simultaneously winding the coils on a plurality of coil forms, the coil forms are placed end-to-end over a cylindrical mandrel, compressed together such, for-example, as by a spring and locking arrangement, and the end one or ones of the forms are positively rotated. Wire conductors are attached as by brazing to respective ones of the terminal members 13, and as the coil forms are rotated the coils 15 and 16, as shown in Fig. 1, are wound thereon. It has been found that because the material of which it is desirable to make the forms 11 has a very smooth surface, during the winding operation the innermost ones of the forms 11 frequently rotate through a lesser angle than the end ones of the forms 11, if they rotate at all. As a result, the coils which are wound on the inner ones of the coil forms do not necessarily consist of as many turns as do the coils which are wound on the end ones of the forms. Also, since this slippage between adjacent ones of the coil forms 11 is not constant, and for other reasons, it is difficult to adjust the winding apparatus to compensate for thi slippage.

In accordance with another aspect of the present invention, both end surfaces of the coil from 11 are serrated at 32 (Figs. 1 through 8, inclusive) so that when a number of coil forms are contiguously arranged on a mandrel, no slippage therebetween can occur and every one of the forms rotates a fixed amount, thereby to provide coils having a fixed number of turns.

In accordance with another aspect of the invention, the upper shoulder of the enlarged cylindrical portion 12 is provided with a plurality of radial notches 35 which, during rotating of the coil forms during the coil winding operation, engage the conductors to prevent them from partially slipping around the form 11, which slippage would result in "coils having different numbers of turns even though the coil forms may be rotated a fixed amount in every case. p

While there has been described what is at present considered to be the preferred embodiments of the invention, it will be understood that various modifications may be made therein'which are within the-true spirit and scope of the invention as defined in the appended claims.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. Means for securing an electrical device to a support member through an aperture in the member, comprising a portion of said device which is adapted to loosely fit within said aperture, means on said device for engaging one side of said support member to prevent movement of said device through said aperture, and outwardly directed protrusions on said portion for engagement with the walls of said aperture and with the other side of said support member, said protrusions being formed of a material which is sufficiently resilient that as said portion is inserted into said aperture said protrusions are deformed and the portions of said protrusions which extend beyond the side of said member opposite to said means return to their original shape after insertion thereof through said aperture, thereby to prevent spurious rotation of said device on said support member.

2. The combination set forth in claim 1 wherein said means on said device for engaging one side of said support comprises a collar.

3. The combination set forth in claim 1 wherein said protrusions comprise a plurality of longitudinal ribs lying parallel to the principal axis of said aperture.

4. Means for securing an electrical device to a support member through an aperture in the member, comprising a portion of said device which is adapted to loosely fit within said aperture, shoulder means on said device for engaging one side of said support member to prevent movement of said device through said aperture, and a plurality of outwardly directed protrusions on said portion for engagement with the walls of said aperture and with the other side of said support member, said protrusions being formed of a material which is sufiiciently resilient that as said portion is inserted into said aperture said protrusions are deformed and the portions of said protrusions which extend beyond the side of said member opposite to said means return to their original shape after insertion thereof through said aperture, thereby to prevent spurious rotation of said device on said support member.

5. The combination set forth in claim 4 which further comprises an annular protrusion spaced from said shoulder, said annular protrusion being formed of a material which is sufiiciently resilient that as said portion is inserted into said aperture said protrusion is compressed to permit passage thereof through said aperture and to cause said annular protrusion to return to its original shape after the insertion thereof through said aperture, said annular protrusion being spaced from said shoulder by a distance equaling the thickness of said support.

References Cited in the file of this patent UNITED STATES PATENTS 1,665,930 Nixon et al. Apr. 10, 1928 1,697,317 Kyle Jan. 1, 1929 1,867,206 Brady July 12, 1932 1,958,126 Bowen May 8, 1934 1,960,227 Krissiep May 22, 1934 1,985,317 Douglas Dec. 18, 1934 2,244,356 Bucklin June 3, 1941 2,244,977 Hansman et al. June 10, 1941 2,476,407 Eriksen et al. July 19, 1949 2,644,978 Becker July 14, 1953 2,649,558 Franz Aug. 18, 1953 2,751,563 Willyard et al. June 19, 1956 2,807,869 Rice Oct. 1, 1957 

